The Universal Mobile Telecommunication System (UMTS) belongs to the 3rd generation communication system; the network part of the UMTS is called UMTS Universal Terrestrial Radio Access Network (UTRAN), and the UTRAN structure is divided into a Radio Access Network (RAN) and a Core Network (CN), wherein the RAN is used for processing all radio-related functions, and the CN processes the switching and routing with an external network of all voice calls and data connections. The two units constitute the whole system together with the UE. A network unit of the RAN includes a Radio Network Controller (RNC) and a transreceiver base station (NodeB). To be able to differentiate each UE in the UTRAN, a UTRAN Radio Network Temporary Identity (U-RNTI) is defined; the length of the U-RNTI is 32 bits, and the U-RNTI is composed of two parts: a Serving RNC (SRNC) Identity (ID) and an SRNC RNTI (S-RNTI), wherein, the SRNC ID represents the serving RNC identity whose meaning is the same as that of an RNC ID, and the S-RNTI represents the RNTI of the SRNC. The SRNC ID is defined as 12 bits, and the S-RNTI is defined as 20 bits; if the SRNC ID has more than 12 bits, then the part exceeding the 12 bits is in the S-RNTI.
When moving between the RNCs, the public UE sends a Cell Update message or a UTRAN Registration Area (URA) Update message to a Drift RNC (DRNC), wherein the message carries the U-RNTI, and then the DRNC resolves, according to the U-RNTI carried in the message, the RNC ID to determine which RNC the message should be sent to. In the current protocol, there are two types of RNC IDs: one is a general RNC ID, which is 12 bits at most, and the other is an extended RNC ID, which can be extended to 16 bits at most; but the DRNC does not know whether the SRNC adopts the general RNC ID or the extended RNC ID, according to the related art, there are several cases as follows: (1) if the target RNC ID is actually the general RNC ID, and the DRNC resolves according to the general RNC ID, then the message will be sent to the target RNC correctly; (2) if the target RNC ID is actually the extended RNC ID, and the DRNC resolves according to the general RNC ID, then the message may be sent to the target RNC correctly or sent incorrectly; (3) if the target RNC ID is actually the extended RNC ID, and the DRNC resolves according to the extended RNC ID, then the message will be sent to the target RNC correctly; (4) if the target RNC ID is actually the general RNC ID, and the DRNC resolves according to the extended RNC ID, then the message will be sent incorrectly. If the message is sent incorrectly, the RNC receiving the message will discard the message, which easily leads to call drop when the UE moves between the RNCs.
In addition, as to an Automatic Neighbour Relation (ANR) function in the UMTS, through a measurement control message which is sent by a network side and received by the UE in a dedicated connection state, information of a new cell is measured and reported to the network side; the reported message includes the Cell ID (C-ID) of the cell in the radio network, and the network side can know, after obtaining the message, which neighbour cells are not configured. The C-ID of the cell in the radio network has 28 bits, including the RNC ID and the C-ID in the RNC; if the RNC finds, according to the C-ID of the cell in the radio network, that the cell is not the one in the RNC, it is needed to send message obtaining information to the other RNC. However, the RNC does not know whether the other RNC adopts 12 bits or 16 bits, according to the related art, there are several cases as follows: (1) if the target RNC ID is actually the general RNC ID, and the DRNC resolves according to the general RNC ID, then the message will be sent to the target RNC correctly; (2) if the target RNC ID is actually the extended RNC ID, and the DRNC resolves according to the general RNC ID, then the message may be sent to the target RNC correctly or sent incorrectly; (3) if the target RNC ID is actually the extended RNC ID, and the DRNC resolves according to the extended RNC ID, then the message will be sent to the target RNC correctly; (4) if the target RNC ID is actually the general RNC ID, and the DRNC resolves according to the extended RNC ID, then the message will be sent incorrectly. If the message is sent incorrectly, the neighbour cells which are not configured by the RNC cannot be identified, which easily leads to call drop when the UE moves between the RNCs.